The present invention relates generally to high pressure grease fittings or check valves used on pumps, valves, flow actuators, compressors, or similar devices. More particularly, the invention relates to high pressure fittings or check valves which prevent clogging or blocking in response to high pressures.
As will be recognized by those skilled in the art, a wide variety of grease fittings have previously been employed to facilitate the introduction of lubricants and the like into equipment. In oil and gas pipeline apparatus, grease is commonly injected under extremely high pressures. Oil and gas equipment generates significant frictional forces, heat, and thermal expansion and contraction. Through time, such forces severely stress the seals, gaskets, and other internal components and undermine the integrity of the equipment. Viscous sealants, lubricants, grease, or the like, may be injected periodically to protect the equipment and prolong equipment life. Those skilled in the art commonly recognize that the viscosity of the sealant, grease, lubricant, or the like, is generally proportional to its sealing and lubricating capability.
"Heavy duty" sealants and lubricants, are quite effective for sealing high pressure equipment. In oil and gas pipeline applications, the force-feeding of "heavy" grease, sealants, or lubricants may necessitate input pressures in excess of 15,000 PSI. Typical high pressure grease fittings such as "button-head" fittings are widely used. A button-head fitting allows the grease or injection gun to be securely fastened within the fitting inlet during introduction of the lubricant.
However, numerous disadvantages are associated with prior art fittings such as button-head fittings and high pressure check valves. No button-head styled fitting known to me will perform consistently and flawlessly. In particular, injection of heavy sealants or lubricants into such prior art grease fittings has proven quite problematic.
Many known prior art fittings in this field of invention employ a "soft seat." This soft seat is formed by a ball, usually of steel construction which forcibly contacts a non-metallic elastomer ring, washer, or cup. The purpose of such a soft seat is to prevent reverse flow from escaping the fitting through the inlet end. In addition, the soft seat prohibits unwanted matter from entering the fitting. However, soft seats wear out quickly when subjected to sustained pressures.
At low pressures, a slight leak will cause the seat to "cut-out" or become grooved, causing permanent leaks. At high pressures, the whole seat can become distorted, thus limiting the usefulness of the fitting. A metal-to-metal seal provides adequate sealing for a pressurized, highly viscous substance. Because soft seals wear out so often, it is common to inject fittings with "bridging agents", minute solid particles which aid in sealing the gaps, cracks, leaks, and holes by collectively joining or spanning the opposing sides of the gap or crack. However, these agents cause other problems.
Besides problems faced with unreliable seals in prior art fittings, numerous other problems result from the injection of heavy substances. Fitting "plug-off" or clogging is related to failure of the usual valve element return spring. In most prior art fittings, the return spring forms a grease flow path through which lubricants or sealants flow. The lubricants flow in through the spring interior and are dispersed through the adjacent spring windings into the equipment being serviced. If the check valve element, typically a sphere, depresses the spring into an overcompressed state, the flow path will be blocked, and the spring may be deformed. In addition, spring twisting and bending can occur unless spring movements are rigorously constrained. A major problem encountered in the prior art is spring "cylinderization," wherein the return spring is compressed until its adjacent windings abut one another, and the spring thus forms a cylinder-like or tube. Cylinderization thus severely restricts grease outflow through the adjacent spring windings.
Additionally, the ball elements common in the vast majority of prior art fittings may reposition themselves atop the compressed spring, so that injection pressures are not properly dissipated. As a result, fitting "blow-out" may occur. "Blow-out" occurs when an induced pressure change in a plugged fitting causes the bottom crimp, or retaining ring to fail, resulting in a sudden drop in pressure as indicated by the grease gun pressure gage. When blow-out does occur, the internal parts of the fitting may be jettisoned into the equipment being serviced. Evacuation or "blow-down" of the attached pipeline or flow line must be initiated in order to facilitate replacement of the collapsed fitting and repair of any damaged equipment. The blow-down process is extremely time-consuming and expensive.
Moreover, if a fitting blows, gas back pressure can result in a calamity. For example, when the grease gun is uncoupled from the fitting, unwanted gas venting may occur. Even if the jammed fitting provides a seal, accumulated bridging agents may prevent full valve closure when grease input pressure is thereafter relaxed. A ruined fitting results. Also, when heavy substances clog and obstruct the lubricant flow paths, the equipment will not be properly lubricated.
Prior art fittings known to me usually plug-off at some time, especially when repeatedly injected with the heavier sealants. Attempts to clear the fitting by increasing the localized pressure within the fitting body will most often result in fitting blow-out. It is thus highly desirable for one to develop a fitting which is immune to spring deformations and fitting plug-off.
The pertinent prior art in this field of invention does not successfully address these problems. U.S. Pat. No. 4,347,915 employs an offset "leg" of the spring member to cause the ball member to drift to one side when the spring compresses. Theoretically, this ball drift increases the size of the flow channel within the axial hollow portion of the spring, and insures that the flow continues. However, when very heavy sealants with large bridging agents are injected into the fitting, the ball forces the leg member to bend downward during spring compression and ultimate cylinderization, permitting the ball member to substantially diminish the flow channel. Hence, this fitting has the propensity to plug-off. The '915 reference also discloses an internal sleeve member which purportedly prolongs the soft seat life. However, the sleeve does virtually nothing to prevent fitting plug-off.
U.S. Pat. Nos. 2,918,084 and 3,437,082 disclose a variety of spring, ball, and sleeve configurations. There is no means suggested in any these patents for preventing deformation of the spring members or plug-off as a result of severely diminished and restricted flow paths.
Hence, it is desired to provide a flow fitting which can withstand high localized pressures and accept very heavy sealants and lubricants for prolonged equipment life. Additionally, a fitting is needed which provides substantially unrestricted flow channels in which the injected sealants, lubricants, or the like, can travel without plugging-off the fitting.